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Date Posted: 00:17:27 03/24/02 Sun
Author: Blue
Author Host/IP: pcd417209.netvigator.com / 203.218.207.209
Subject: Some AL questions

1. .If a man moves from the earth to the moon, will the maximum weight that
he can lift change? and why?

2. A spacecraft orbiting round the earth in a certain circular radius r0
with a speed v0 ignites its rocket to increase its speed. Which of the
following statements concerning its subsequent motion is/are correct?
(a) Its total energy increase
(b) It will finally stay in a new orbit with radius r>r0
(c) It will finally move with a speed v>v0

The answer is (1) & (2)

But why (b) is correct?
GMm/r^2 = mv^2/r
so GM=rv^2 which is constant
So if v increase, r should be decrease, right??
And why did the final speed not greater than inital speed???

3. In an arrangement for viewing the interference pattern of an air wedge
formed by 2 glass sheet, which of the following statemnets is correct?
(c) If white light is used, the second bright fringe and the third bright
fringe would overlap. <---This statement is correct but i don't understand
why this will happen?

4. Two parallel metal plates are connected to the battery. If one of the
plate is moved towards another, which of the following statements is
correct?
(a) Charges stored in the plates increased.
(b) The electrical potential energy of the 2 plates is increased.
(c) Work is done on the system in moving one of the plates towards the
other.
The answer is (a)and (b). Why (c) is not correct?? If work is not done, then
where does the extra electrical potential energy of the plates come from? Is
it come from the power supply?

5. In the Hall effect, do we need to know the sign of charge carriers in the
metal slice in order to decide which surface of the slice is at a higher
potential? But as I have seen, usually we do not know whether the charge
carries are positive or negative, (in the quesiton it usually just states it
is a metal or it is copper) then how can we decide the direction of E-field?

6. When a light rectangular wire frame moves with a uniform velocity to the
right across a region of uniform magnetic field, is an applied force
required to move the wire frame? If it is required, is it always true that
it will be in a direction opposite to the magnetic force in the wire frame?
If an applied force is not required, then will the wire frame accelerate??

7. If 2 different gases have same pressure in 2 separate identical
containers at the same temperature, is the frequency of collision of gas
molecules with the walls of the two containers the same?

8.In an experiment to measure thickness of the metal sheet in a circular
tube, the external diameter d1 is (64 +- 2) mm and the internal diameter d2
is (47+- 1)mm. The maximum percentage error in the calculation of d2-d1 is:

My method is : 2/64 x100% + 1/47 x100 % = 5%

But the answer is (2+1) / (64-17) x 100% = 18%

Why is my method wrong?

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